The current proposal tests the central hypothesis that acetaminophen will attenuate the oxidative stress response associated with CPB-induced hemolysis in children undergoing cardiac surgery. If acetaminophen attenuates the oxidative stress response associated with CPB-induced hemolysis the potential therapeutic benefit extends to all cardiac surgery patients requiring CPB. Based on the outcome of this pilot study we will design a prospective randomized trial to test the hypothesis that acetaminophen will reduce AKI associated with hemoprotein-induced oxidative stress following CPB.